碱法提高铝硅矿物的铝硅比

采用NaOH溶液时铝硅矿物进行预脱硅处理,测出溶渣中SiO2和Al1O3的含量,计算得出渣中的铝硅比.考察液固比、溶出温度、溶出时间、碱浓度等因素对铝硅矿物溶出后渣中铝硅比的影响.实验表明,在液固比为40∶1、温度95℃、溶出时间3 h、40%碱浓度条件下,矿物的脱硅率可达55%以上.预脱硅后渣中铝硅比由0.89提高到...     

高铝粉煤灰预脱硅碱溶提铝过程中的物相转变规律

采用化学分析和XRF、XRD、激光粒度仪、SEM、FT-IR分析技术,研究了高铝粉煤灰预脱硅及浓碱液提铝过程中的固相变化规律.结果表明,高铝粉煤灰经预脱硅及NaOH浓碱溶液溶出后,碱灰质量比大于6时,Al2O3的溶出率大于85%,尾灰中铝硅质量比降至0.21,铝硅选择性分离.预脱硅过程中莫来石相和刚玉相未被破坏,而所含无定型铝硅酸盐溶解形成羟基方钠石Na8Al6Si6O24(OH)2(H2O)2,并附着于颗粒表面导致中值粒径略有增加;浓碱溶液提铝过程中,莫来石及刚玉相完全溶解,形成规则柱状或杆状的NaCaHSiO4及类沸石1.2Na2O’0.8CaO’Al2O3’2SiO2’H2O,中值粒径减小.     

水热法由富锰渣制备4A分子筛工艺初探

研究了由富锰渣制备锰的过程中产生的硅铝废渣(酸浸渣)制备4A分子筛的工艺.以浓硫酸为浸取介质,将富锰渣中锰、铁、钙、镁等可溶性物质溶出,过滤所得固相酸浸渣在反应釜器中150℃、0.4MPa下与碱反应将硅铝溶出,以分析纯Al(OH)3,为铝源,补铝调整比例到4A分子筛合适的硅/铝比,使溶液中各物质摩尔比为SiO2/Al2O3≈2,H2O/Na2O≈28,Na2O/SiO2≈0.9.浓缩溶液至过饱和状态,加入EDTA.将过饱和状态的溶液在90℃恒温5h左右,加入NaCl少许,放冷使之结晶.过滤并洗涤晶体至pH值至9～10,在烘箱中105℃干燥,于马弗炉中5000℃右煅烧1h脱水,即得4A分子筛产品.研究了EDTA对结晶母液中有色离子的络合效果,结果表明对Fe3 有一定去除效果.由XRD分析,产品主要成分为4A分子筛,但还有杂晶.     

NaOH亚熔盐法处理拜尔法赤泥的铝硅行为

针对拜尔法赤泥铝/硅比偏高的问题,对NaOH亚熔盐法处理拜耳法赤泥过程中的Al, Si行为进行了研究. 考察了溶出温度、碱/泥比、添加CaO等主要因素对终赤泥化学成分和物相结构的影响. 结果表明,溶出温度高、碱/泥比大有利于Al2O3的回收,相应的终赤泥的铝/硅比较低. 在碱/泥比6、溶出温度230℃、时间2 h的条件下,氧化铝回收率可达79.22%,终赤泥的铝/硅比可降到0.39,终赤泥中的硅主要以NaCaHSiO4和Ca3(Fe0.87Al0.13)2(SiO4)1.65(OH)5.4形式存在. 在处理CaO/SiO2>1.2的拜尔法赤泥时继续添加CaO并不能继续提高Al2O3的回收率.     

高铝粉煤灰碳酸钠焙烧与酸浸提铝的动力学

以内蒙古高铝粉煤灰(Al2O3/SiO2质量比1.24)为原料,采用Na2CO3焙烧活化-盐酸浸取法提铝,考察了焙烧温度、时间和碳酸钠/粉煤灰质量比的影响,对焙烧活化及酸浸提铝动力学进行研究,分析了提铝机理. 结果表明,高温活化条件下,粉煤灰中的莫来石及SiO2与Na2CO3反应生成NaAlSiO4, Al2O3和Na2SiO3,酸浸后铝浸出率超过94.99%;活化过程符合Crank-Ginstling-Braunshtein模型,表观活化能为117.06 kJ/mol,活化反应受固膜扩散控制.     

硅酸钠溶液合成托贝莫来石晶须

以硅酸钠为硅质原料,研究了动态水热法合成托贝莫来石的条件及其对产物纯度和形貌的影响。结果表明:硅酸钠和石灰乳直接反应合成的产物主要为针钠钙石;而在苛性碱溶液中反应时,针钠钙石向生成托贝莫来石的方向转化,随苛性碱浓度提高,托贝莫来石生成量增加;加入铝离子且其含量达到钙铝摩尔比为5时,可获得纯的1.1 nm托贝莫来石;溶液中的氯离子可促进晶须生长,当钙氯摩尔比为5时,托贝莫来石晶须的长度为2～13μm,直径为0.2～0.5μm。在优化的合成条件下,以实际含硅碱液为原料,合成出长度为2～10μm、直径为0.2～1.0μm的托贝莫来石晶须。在合成托贝莫来石过程中,苛性碱改变了水化硅酸钙的生成环境,铝离子使硅氧四面体双链无法形成而得到四面体单链,最终合成出纯的1.1 nm托贝莫来石;而氯离子所产生的盐效应促进了托贝莫来石结晶长大,有助于制备组分单一、结晶晶面完整的托贝莫来石晶须。     

微波法由富锰渣制备4A分子筛

研究了以富锰渣为原料制备分子筛的工艺.作者以浓硫酸为浸取介质,在90～100 ℃下反应3 h,将富锰渣中锰、铁、钙、镁等可溶性物质溶出,液相中的锰用来制备硫酸锰.过滤所得固相酸浸渣在微波反应器中与碱反应将硅铝溶出,以分析纯Al(OH)3为铝源,补铝调整比例到4 A分子筛合适的硅/铝比,使溶液中各物质摩尔比为SiO2/Al2O3≈2,H2O/Na2O≈28,Na2O/SiO2≈0.9.浓缩溶液至过饱和状态,为结晶做准备.将过饱和状态的溶液放在空气中冷却到30 ℃,稍等片刻,再升温至90 ℃左右,恒温5 h左右,加入NaCl少许,放冷使之结晶.过滤并洗涤晶体至pH值至9～10,于马弗炉中500 ℃左右煅烧1 h脱水,即得4A分子筛产品.4A分子筛的质量指标符合GB1768-93,XRD分析与文献数据基本吻合.     

碳酸钠焙烧铝系钒铁炉渣共提取钒与铝

通过对铝系钒铁炉渣碳酸钠焙烧-水浸全过程的矿物分析、热力学计算及对比实验,研究了炉渣中钒、铝同步转化、溶出的机理与规律. 结果显示,焙烧进程中渣中镁铝尖晶石MgO×Al2O3相、CaO×2Al2O3相逐渐消失,MgO相生成,并生成碱熔相Na2O×Al2O3和钒酸盐. 随焙烧温度及时间增加,Na2O×Al2O3和钒酸盐相明显增多,钒、铝溶出率增加. 焙烧熟料经水浸后,液相呈碱性,钒、铝分别以可溶性钒酸钠和铝酸钠的形式进入水相,固相残留物为少量未反应的镁铝尖晶石及新生成的MgO和Ca(OH)2. 在磨矿粒度<75 mm、配碱系数1.0、焙烧温度1000℃及焙烧时间4 h的优化条件下,钒的溶出率可达90%,铝的溶出率可达75%.     

危废焚烧炉用Al2O3-Cr2O3-ZrO2砖抗渣侵蚀性及六价铬形成研究

Al2O3-Cr2O3-ZrO2砖具有较优良的抗渣侵蚀性能和力学性能,被作为内衬材料应用于危废垃圾焚烧炉.然而,危废垃圾来源广,成分复杂,其焚烧所产生的渣对砖的侵蚀程度及机理也必然不同.此外,砖中的Cr2O3在高温下可能氧化为含Cr(Ⅵ)的有害物质.为此,通过静态抗渣实验研究了四种不同组成危废灰渣对Al2O3-Cr2O3-ZrO2砖的侵蚀过程及机理,并通过浸出实验研究了熔渣对砖中Cr(Ⅵ)形成的影响.结果 表明:不同渣对Al2O3-Cr2O3-ZrO2砖的侵蚀程度及机理各不相同.高钙渣A侵蚀过程中,生成了高熔点的CA6、Ca2Al2SiO7和Ca2SiO4相,在一定程度上减缓了渣的侵蚀速度,砖体表现出最好的抗侵蚀性.高铁渣D侵蚀过程中生成熔点较低的CaFe2O4相,加之砖中Al2O3在Fe2O3-SiO2渣中的溶解度较高,因此高铁渣D对砖体的侵蚀程度最严重.高硅渣B和C侵蚀过程中主要生成钙铝黄长石新相,渣对砖体的侵蚀程度居中.不同的渣侵蚀后,渗透层中的Cr(Ⅵ)含量均增加,且渣的组成对Cr(Ⅵ)含量影响较大.由于CaO能显著促进Cr(Ⅲ)氧化为Cr(Ⅵ),高钙渣A侵蚀后,渗透层中的Cr(Ⅵ)含量最高,为84.7 mg/kg.SiO2可优先与CaO和Na2O等碱金属氧化物反应生成稳定化合物,高硅渣B和C侵蚀后,渗透层中的Cr(Ⅵ)含量较低,分别为9.9 mg/kg和13.6 mg/kg.对于高铁渣D,浸出过程会有含Cr(Ⅵ)的水化相(3CaO· Al2O3·CaCrO4·nH2O)形成,降低了Cr(Ⅵ)的浸出能力.     

碱激发剂中钠、硅对CFB飞灰合成地聚物的影响

以偏高岭土掺加石灰石和石膏模拟循环流化床(CFB)飞灰,研究了不同SiO2/Al2O3和Na2O/Al2O3对烧粘土材料合成地聚物过程中,凝结时间和抗压强度的变化规律;借助X射线衍射和拉曼图谱分析,证明了CFB合成地聚物过程中存在10种主要化学反应.同时发现:碱激发剂中钠含量变化主要影响活性硅、铝单体数量的多少,活性硅含量增加更有利于生成CSH和(Na,Ca)-PSS型地聚物;在SiO2-Al2O3-CaO-Na2O体系中,当Na2O/Al2O3≥1.1时,反应体系因生成水化石榴石而改变地聚反应历程,进而对样品抗压强度产生负效应;SiO2/Al2O3≥3.0时,样品凝结迅速,不利搅拌.     

硅藻精土制备硅酸钠工艺研究

硅藻土的主要化学成分是非晶质二氧化硅。以临江低品位硅藻土矿选矿精土为原料,采用水热碱溶法进行碱溶制备硅酸钠工艺的研究。以硅藻精土中二氧化硅的溶出率以及制得硅酸钠的硅钠比作为评价指标,研究了碱溶时间、碱溶温度、液固质量比以及碱土质量比对二氧化硅溶出率和硅酸钠硅钠比的影响规律。结果表明,在其他条件相同的情况下,碱土比越大,二氧化硅溶出率越高,硅酸钠的硅钠比越小。在碱溶时间为90 min、碱溶温度为 96 ℃、液固质量比为2.5、碱土质量比为1.24条件下,二氧化硅的溶出率为93.22%,硅酸钠的硅钠比为0.96,硅酸钠的产出率为100 g硅藻精土可制得硅酸钠169.35 g。     

煤矸石酸浸废渣制备白炭黑的工艺研究

白炭黑是白色粉末状无定形硅酸和硅酸盐产品的总称,其用途十分广泛。煤矸石酸浸提铝后所得废渣中含有大量的二氧化硅（质量分数为80%~90%）,以其为原料制备白炭黑可有效利用资源,变废为宝。研究以煤矸石提铝废渣与碳酸钠在750~850 ℃下熔融反应、200 ℃下高压水溶得到硅酸钠溶液,通过碳分制得白炭黑。实验得到最佳碳分工艺条件：硅酸钠硅钠比为1.5（Na2O与SiO2物质的量比）、硅酸钠质量浓度为1.07 g/cm3、添加剂乙醇为4 mol/L、聚乙二醇（PEG）为1.11×10-5 mol/L、十六烷基三甲基溴化铵（CTAB）为9×10-4 mol/L。结果表明,在最佳条件下得到的白炭黑产品性能最佳。     

Hydrothermal reaction between C6S6H and kaolinite for the formation of tobermorite at 180°C

11 Å tobermorites were made from CSH (Ca/Si = 1.14) and kaolinite with Ca/(Si+Al) = 0.8 and Al/(Si+Al)= 0.15 at 180°C. The CSH was prepared from colloidal silica and lime at 130°C and 180°C for 2 h. Reaction gives in succession CSH, poorly crystalline Al-substituted tobermorite, and highly crystalline Al-substituted tobermorite. The addition of kaolinite markedly accelerates the formation of tobermorite within 4 h, more effectively with CSH prepared at 130°C than with that prepared at 180°C. X-ray fluorescence diffractometry shows that the Al coordination number is a mixture of 4 and 6 in the initial products and shifts to 4 with an increase in processing time. This agrees with the results for the degree of reaction of the kaolinite.     

Structural Degradation of Tobermorite during Vibratory Milling

Mechanochemistry of hydrothermally prepared Al-free and Al-substituted 1.1 nm tobermorite was studied using ²⁹Si NMR, XRD, and TGA-DTA. Tobermorite has a double-chain structure and Al/Si substitution occurs preferentially at bridging tetrahedra. By using the vibration mill, both tobermorites were observed to decompose as a function of milling time to form amorphous C-S-H-like phases. The decomposition rate was higher for the Al-substituted tobermorite. The decomposition process occurs mainly at the bridge portion of the silicate double chain. In the Al-substituted tobermorite, the breakage seems to occur preferentially at the points where Al has replaced Si. On heating the amorphous C-S-H-like phase, wollastonite is formed. However, no decrease was observed at the wollastonite formation temperature.     

从含碱硅酸钠溶液中水热合成硅灰石

以含碱硅酸钠溶液为原料,在常压下加入石灰乳,先水热合成CaO·SiO2·H2O,再将CaO·SiO2·H2O在850℃下焙烧2 h可制备硅灰石.研究了溶液中SiO2浓度、钙硅摩尔比(C/S)及反应时间对硅灰石合成的影响.热力学计算结果表明,常压下Na2O-CaO-SiO2-H2O体系中,最有可能形成CaO·SiO2·H2O及2CaO·SiO2·1.17H2O.实验结果表明:当C/S为1.0时,随着溶液中硅浓度的增加,硅酸根离子的聚合程度增加,有利于硅灰石的制备;随着时间的延长,硅灰石结晶程度越高;当C/S为0.6、0.8、1.0时,最终产物为CaSiO3;当C/S为1.5、2.0时,最终产物中含有大量的Ca2SiO4.适宜的水热合成条件为:SiO2浓度>30 g/L、C/S 0.6～1.0、温度98℃、反应时间>3 h.     

Crystallization and phase transition of tobermorite synthesized by hydrothermal reaction from dicalcium silicate

In this paper, tobermorite was hydrothermally synthesized from the dicalcium silicate (C₂S) in sodium silicate solution, and the crystallization and phase transition process were investigated in detail using XRD, Raman spectra, and SEM. The tobermorite is difficult to synthesize when the temperature is lower than 160°C because it gets converted into xonotlite (without Na₂O) or pectolite (with Na₂O) when the temperature is higher than 180°C. The crystallization process of tobermorite shows “S” trend with the increase in time, which can be divided into three stages: the nucleation stage, rapid crystal growth stage, and perfect crystal forming stage. During the crystallization, 90% of the crystallization of tobermorite is completed in the stage of rapid crystal growth. Raman spectra and SEM analysis show that with the increase in hydrothermal time, the C₂S of monomer (Q⁰) is first converted into the calcium silicate hydrate of sheet (Q² and Q³), and then continues to convert into tobermorite of chain (Q²).     

新型采空区填充注浆材料的研制与性能试验研究

为探索碱渣利用新途径,研制开发了针对于采空区填充的碱渣-粉煤灰体系注浆材料.通过正交试验研究了粉煤灰与碱渣质量比(A)、液固比(B)与硅酸钠溶液浓度(C)对浆液主要性能的影响;并优选基础配比,利用石膏部分替代硅酸钠进行优化试验.结果表明:初凝时间受因素A影响最大,因素C对终凝时间及抗压强度影响最显著,流动度主要由因素B与因素C控制,析水率与结石率主要受因素A和因素B的影响;石膏替代量的变化对凝结时间、流动度和强度有显著影响.碱渣、粉煤灰、硅酸钠、石膏与水质量之比为1:1:1.04:0.26:1.65时,浆液综合性能最佳,满足采空区填充技术要求.     

Influence of SiO2 modification on hydrogarnets formation during hydrothermal synthesis

Formation and stability of hydrogarnet and Al-substituted tobermorite were examined at 175 °C temperature in saturated steam environment processing CaO-quartz and CaO-amorphous SiO₂ suspensions. A large quantity of Al₂O₃ was added to the starting mixtures [molar ratio A/(S+A)=0.10, duration of hydrothermal synthesis—from 0 to 24 h]. It was determined that hydrogarnets always tend to form more rapidly than 1.13 nm tobermorite. However, later, with extension of synthesis duration, they start to fracture and their quantity reduces almost in half during 24 h. CaO is present in the further reaction with SiO₂ forming hydrated calcium silicates, and released Al³⁺ ions are inserted into Al-substituted tobermorite crystal lattice. Using amorphous SiO₂·nH₂O as SiO₂ component, starting raw materials react considerably quicker—the total Ca(OH)₂ is joined already while increasing the temperature up to 175 °C. Meanwhile, in the mixtures with quartz when their composition is described by the molar ratio C/(S+A)=1.0, traces of Ca(OH)₂ are found even after 24-h isothermal treatment at 175 °C temperature. Moreover, it depends on SiO₂ modification the hydrogarnets of what type are to be formed. Si-free hydrogrossular forms in the mixtures with quartz and katoite in the mixtures with SiO₂·nH₂O. Si⁴⁺ ions are inserted into the crystal lattice of the latter compound while the first one remains undisturbed. This is presumably related to the lower solubility of the quartz. It was also noticed that an isomorphic Si⁴⁺ ions substitution with Al³⁺ ions in the hydrated calcium silicate lattice is considerably quicker when an amorphous SiO₂ is used as SiO₂ component instead of quartz.     

Hydrothermal reaction between CSH and kaolinite for the formation of tobermorite at 180°C

11 Å tobermorites were made from C---S---H (Ca/Si = 1.14) and kaolinite with Ca/(Si+Al) = 0.8 and Al/(Si+Al)= 0.15 at 180°C. The C---S---H was prepared from colloidal silica and lime at 130°C and 180°C for 2 h. Reaction gives in succession C---S---H, poorly crystalline Al-substituted tobermorite, and highly crystalline Al-substituted tobermorite. The addition of kaolinite markedly accelerates the formation of tobermorite within 4 h, more effectively with C---S---H prepared at 130°C than with that prepared at 180°C. X-ray fluorescence diffractometry shows that the Al coordination number is a mixture of 4 and 6 in the initial products and shifts to 4 with an increase in processing time. This agrees with the results for the degree of reaction of the kaolinite.     

Structural changes in C–S–H gel during dissolution: Small-angle neutron scattering and Si-NMR characterization

Flow-through experiments were conducted to study the calcium–silicate–hydrate (C–S–H) gel dissolution kinetics. During C–S–H gel dissolution the initial aqueous Ca/Si ratio decreases to reach the stoichiometric value of the Ca/Si ratio of a tobermorite-like phase (Ca/Si = 0.83). As the Ca/Si ratio decreases, the solid C–S–H dissolution rate increases from (4.5 × 10^− 14 to 6.7 × 10^− 12) mol m^− 2 s^− 1. The changes in the microstructure of the dissolving C–S–H gel were characterized by small-angle neutron scattering (SANS) and ²⁹Si magic-angle-spinning nuclear magnetic resonance (²⁹Si-MAS NMR). The SANS data were fitted using a fractal model. The SANS specific surface area tends to increase with time and the obtained fit parameters reflect the changes in the nanostructure of the dissolving solid C–S–H within the gel. The ²⁹Si MAS NMR analyses show that with dissolution the solid C–S–H structure tends to a more ordered tobermorite structure, in agreement with the Ca/Si ratio evolution.